This invention relates generally to semiconductor structures and polarization modulator devices and to a method for their fabrication, and more specifically to semiconductor structures and polarization modulator devices and to the fabrication and use of semiconductor structures, devices, and integrated circuits that include a monocrystalline material layer comprised of semiconductor material, compound semiconductor material, and/or other types of material such as metals and non-metals.
Semiconductor devices often include multiple layers of conductive, insulating, and semiconductive layers. Often, the desirable properties of such layers improve with the crystallinity of the layer. For example, the electron mobility and band gap of semiconductive layers improves as the crystallinity of the layer increases. Similarly, the free electron concentration of conductive layers and the electron charge displacement and electron energy recoverability of insulative or dielectric films improves as the crystallinity of these layers increases.
For many years, attempts have been made to grow various monolithic thin films on a foreign substrate such as silicon (Si). To achieve optimal characteristics of the various monolithic layers, however, a monocrystalline film of high crystalline quality is desired. Attempts have been made, for example, to grow various monocrystalline layers on a substrate such as germanium, silicon, and various insulators. These attempts have generally been unsuccessful because lattice mismatches between the host crystal and the grown crystal have caused the resulting layer of monocrystalline material to be of low crystalline quality.
If a large area thin film of high quality monocrystalline material was available at low cost, a variety of semiconductor devices could advantageously be fabricated in or using that film at a low cost compared to the cost of fabricating such devices beginning with a bulk wafer of semiconductor material or in an epitaxial film of such material on a bulk wafer of semiconductor material. In addition, if a thin film of high quality monocrystalline material could be realized beginning with a bulk wafer such as a silicon wafer, an integrated device structure could be achieved that took advantage of the best properties of both the silicon and the high quality monocrystalline material.
Accordingly, a need exists for a semiconductor structure that provides a high quality monocrystalline film or layer over another monocrystalline material and for a process for making such a structure. In other words, there is a need for providing the formation of a monocrystalline substrate that is compliant with a high quality monocrystalline material layer so that true two-dimensional growth can be achieved for the formation of quality semiconductor structures, devices and integrated circuits having grown monocrystalline film having the same crystal orientation as an underlying substrate. This monocrystalline material layer may be comprised of a semiconductor material, a compound semiconductor material, and other types of material such as metals and non-metals.
Present devices for arbitrary polarization generation use phase shifting and amplitude attenuation networks. Such networks are typically slow for precision. Slow components restrict the information transfer rate, so that polarization modulation is not practical for most applications. In addition, polar modulation is restricted to limited states of polarization and cannot reverse polarization. Polarization can be visualized using a Poincare sphere, which represents all states of polarization. Each point on the surface of the sphere corresponds to a state of polarization. Linear polarization is represented by the points on the equator and circular polarization is represented by the two poles. Present devices operating in one hemisphere of the Poincare sphere, such as the northern hemisphere, cannot readily switch to the opposite, southern hemisphere.
Accordingly, a need exists for a polarization modulator providing variable polarization over all states of polarization to maximize signal reception or transmission, regardless of antenna orientation. Further, the need exists for a polarization modulator providing polar modulation over all states of polarization to provide additional information transfer capability.